You've left the geanie so much room for interpretation, for example:

• Take 30 seconds to do the task of giving all blind people eyesight.
• You didn't say when these 30 seconds happen. Could be all at once now, but could also be everyone at their last 30 seconds to live.
• "Eyesight" could mean that there are eyes sighting the blind one. So there's just someone around that looks at the blind person.
• You didn't say that the people have to be alive. So now, they become zombies for 30 seconds. This means somewhere where there's a living human next to a dead blind human, the living one gets bitten, and the zombie disease can spread.